Friday's predawn attacks came after a number of recent media reports on Greece's "triangle of power," providing detailed accounts of the strong links among the country's financial and political elite and the media.

The Greek government has condemned the attacks. Spokesman Simos Kedikoglou said they were "an attempt to terrorize the media," which he described "as a vital part of our democracy".

It is the second time the group has targeted journalists. In July, it also claimed responsibility for an arson attack outside a restaurant owned by a prominent Greek journalist.

Greece's international partners agreed on a second bailout program late last year, and gave the government elected in June more time to meet its budget commitments.

But the austerity measures imposed to tackle the country's debt crisis have provoked violent protests in recent months and mass strikes by public and private sector workers.

The Greek economy has shrunk by about a fifth since 2008, adding more than 500,000 people to the jobless total in a country with a population of 10 million. The unemployment rate has more than tripled over the same period and stood at 26% as of September.